From DE 198 21 164A1 has become known a typical six-gear dual-clutch transmission in which two fixed wheels are situated upon a first input shaft designed as hollow shaft. While the first fixed wheel is in tooth contact with the idler wheel for the reverse gear and a second idler wheel for the second gear, the second fixed wheel meshes with one idler wheel for the sixth gear and with one idler wheel for the fourth gear. In addition, the idler wheels for the reverse gear and the sixth gear are supported in the transmission upon a first countershaft while the idler wheels for the second gear and the fourth gear are placed upon a second countershaft. This dual-clutch transmission has a comparatively short construction so that it can be used for crosswise installation in a motor vehicle.
From DE 199 23 185 A1 has further become known a dual-clutch transmission in which both, upon a hollow first input shaft and upon the second input shaft, are supported therein and designed as solid shaft, a respective fixed wheel is situated which drives each of two idler wheels of different transmission gears. The first fixed wheel situated upon the hollow shaft thus meshes with the idler wheel for the third gear and the idler wheel for the fifth gear. The second fixed wheel situated upon the solid shaft is, on the other hand, in tooth contact with the idler wheels for the second and for the fourth gears.
With this background, the problem on which the invention is based is to introduce a structure for dual-clutch transmissions which can be used both in a six-gear transmission and in a seven-gear transmission. Besides, a six-gear transmission thus built must be shorter than the known generic transmission drafts and the seven-gear dual-clutch transmission must fit in a similar vehicle installation space which hitherto had been adequate only for dual-clutch transmission having less gears. Finally, by reducing the hitherto needed transmission parts, the production cost is lowered.